Magnetic recording head and magnetic recording apparatus

ABSTRACT

A magnetic recording head includes: a main magnetic pole; a laminated body; and a pair of electrodes. The laminated body includes a first magnetic layer having a coercivity lower than magnetic field applied by the main magnetic pole, a second magnetic layer having a coercivity lower than the magnetic field applied by the main magnetic pole, and an intermediate layer provided between the first magnetic layer and the second magnetic layer. The pair of electrodes are operable to pass a current through the laminated body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 12/155,329,filed Jun. 2, 2008 and claims the benefit of priority from the priorJapanese Patent Application No. 2007-215594, filed on Aug. 22, 2007; theentire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a magnetic recording head and a magneticrecording apparatus provided with a spin torque oscillator, suitable forusing a high-frequency assist magnetic field to realize data storagewith high recording density, high recording capacity, and high datatransfer rate.

2. Background Art

In the 1990s, the practical application of MR (magnetoresistive effect)heads and GMR (giant magnetoresistive effect) heads triggered a dramaticincrease in the recording density and recording capacity of HDD (harddisk drive). However, in the early 2000s, the problem of thermalfluctuations in magnetic recording media became manifest, and hence theincrease of recording density temporarily slowed down. Nevertheless,perpendicular magnetic recording, which is in principle moreadvantageous to high-density recording than longitudinal magneticrecording, was put into practical use in 2005. It serves as an enginefor the increase of HDD recording density, which exhibits an annualgrowth rate of approximately 40% these days.

Furthermore, the latest demonstration experiments have achieved arecording density exceeding 400 Gbits/inch². If the developmentcontinues steadily, the recording density is expected to achieve 1Tbits/inch² around 2012. However, it is considered that such a highrecording density is not easy to achieve even by using perpendicularmagnetic recording because the problem of thermal fluctuations becomesmanifest again.

As a recording scheme possibly solving the above problem, the “microwaveassisted magnetic recording scheme” is proposed. In the microwaveassisted magnetic recording scheme, a high-frequency magnetic field nearthe resonance frequency of the magnetic recording medium, which issufficiently higher than the recording signal frequency, is locallyapplied. This produces resonance in the magnetic recording medium, whichdecreases the coercivity (Hc) of the magnetic recording medium subjectedto the high-frequency magnetic field to less than half the originalcoercivity. Thus, superposition of a high-frequency magnetic field onthe recording magnetic field enables magnetic recording on a magneticrecording medium having higher coercivity (Hc) and higher magneticanisotropy energy (Ku) (e.g., U.S. Pat. No. 6,011,664, hereinafterreferred to as Patent Document 1). However, the technique disclosed inPatent Document 1 uses a coil to generate a high-frequency magneticfield, and it is difficult to efficiently apply a high-frequencymagnetic field during high-density recording.

Techniques based on a spin torque oscillator are also proposed as ameans for generating a high-frequency magnetic field (e.g., US PatentApplication Publication No. 2005/0023938, hereinafter referred to asPatent Document 2; US Patent Application Publication No. 2005/0219771,hereinafter referred to as Patent Document 3). In the techniquesdisclosed in Patent Documents 2 and 3, the spin torque oscillatorcomprises a spin injection layer, an intermediate layer, a magneticlayer, and electrodes. When a DC current is passed through the spintorque oscillator via the electrode, the spin torque generated by thespin injection layer produces ferromagnetic resonance in themagnetization of the magnetic layer. Consequently, a high-frequencymagnetic field is generated from the spin torque oscillator.

Because the spin torque oscillator has a size of approximately severalten nanometers, the generated high-frequency magnetic field is localizedwithin approximately several ten nanometers around the spin torqueoscillator.

Furthermore, the perpendicularly magnetized magnetic recording mediumcan be efficiently resonated by the longitudinal component of thehigh-frequency magnetic field, allowing a significant decrease in thecoercivity of the magnetic recording medium. Consequently, high-densitymagnetic recording is performed only in a portion where the recordingmagnetic field of the main magnetic pole is superposed on thehigh-frequency magnetic field of the spin torque oscillator, allowingutilization of magnetic recording media having high coercivity (Hc) andhigh magnetic anisotropy energy (Ku). Thus the problem of thermalfluctuations during high-density recording can be avoided.

SUMMARY OF THE INVENTION

According to an aspect of the invention, there is provided a magneticrecording head including: a main magnetic pole; a laminated bodyincluding a first magnetic layer having a coercivity lower than magneticfield applied by the main magnetic pole, a second magnetic layer havinga coercivity lower than the magnetic field applied by the main magneticpole, and an intermediate layer provided between the first magneticlayer and the second magnetic layer; and a pair of electrodes operableto pass a current through the laminated body.

According to another aspect of the invention, there is provided amagnetic recording apparatus including: a magnetic recording medium; themagnetic recording head including: a main magnetic pole; a laminatedbody including a first magnetic layer having a coercivity lower thanmagnetic field applied by the main magnetic pole, a second magneticlayer having a coercivity lower than the magnetic field applied by themain magnetic pole, and an intermediate layer provided between the firstmagnetic layer and the second magnetic layer; and a pair of electrodesoperable to pass a current through the laminated body; a movingmechanism configured to allow relative movement between the magneticrecording medium and the magnetic recording head which are opposed toeach other with a spacing therebetween or in contact with each other; acontroller configured to position the magnetic recording head at aprescribed recording position of the magnetic recording medium; and asignal processing unit configured to perform writing and reading of asignal on the magnetic recording medium by using the magnetic recordinghead.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the schematic configuration of amagnetic recording head according to an embodiment of the invention;

FIG. 2 is a perspective view showing a head slider on which the magneticrecording head is mounted;

FIG. 3 is a schematic view illustrating the structure of a spin torqueoscillator 10 provided in this magnetic recording head;

FIGS. 4A to 4D show graphs illustrating the write operation of themagnetic recording head provided with the spin torque oscillator 10shown in FIG. 3;

FIGS. 5A to 5D show graphs illustrating the write operation of amicrowave assisted magnetic head according to a comparative example;

FIG. 6 is a conceptual view for illustrating the operation of themagnetic recording head of this embodiment;

FIG. 7 is a conceptual view for illustrating the operation of themagnetic recording head of this embodiment;

FIG. 8 is a conceptual view for illustrating the relationship betweenthe current direction in the spin torque oscillator and the operation ofthe magnetic recording head;

FIG. 9 is a conceptual view for illustrating the relationship betweenthe current direction in the spin torque oscillator and the operation ofthe magnetic recording head;

FIG. 10 is a perspective view showing the schematic configuration of amagnetic recording head according to a second embodiment of theinvention;

FIG. 11 is a conceptual view for illustrating the operation of themagnetic recording head of the second embodiment;

FIGS. 12A to 12D show graphs illustrating the write operation of themagnetic recording head provided with the spin torque oscillator 10shown in FIG. 11;

FIG. 13 is a perspective view showing the schematic configuration of amagnetic recording head according to a third embodiment of theinvention;

FIG. 14 is a conceptual view for illustrating the operation of themagnetic recording head of the third embodiment;

FIG. 15 is a perspective view showing the schematic configuration of amagnetic recording head according to a fourth embodiment of theinvention;

FIG. 16 is a graph illustrating the relationship between a magnetizationinversion time and a damping constant;

FIG. 17 is a perspective view showing the schematic configuration of amagnetic recording head according to a fifth embodiment of theinvention;

FIG. 18 is a conceptual view illustrating a characteristic of spintorque in the magnetic recording head according to the fifth embodimentof the invention;

FIG. 19 is a perspective view showing the schematic configuration of amagnetic recording head according to a sixth embodiment of theinvention;

FIG. 20 is a graph illustrating a characteristic of the magneticrecording head according to the sixth embodiment of the invention;

FIG. 21 is a perspective view showing the schematic configuration of amagnetic recording head according to a seventh embodiment of theinvention;

FIG. 22 is a perspective view showing the schematic configuration of amagnetic recording head according to an eighth embodiment of theinvention;

FIG. 23 is a perspective view showing the schematic configuration of amagnetic recording head according to a ninth embodiment of theinvention;

FIG. 24 is a principal perspective view illustrating the schematicconfiguration of a magnetic recording/reproducing apparatus according toa tenth embodiment of the invention;

FIG. 25 is an enlarged perspective view of a magnetic head assemblyahead of an actuator arm 155 as viewed from the disk side;

FIG. 26 is a schematic view illustrating a magnetic recording mediumthat can be used in this embodiment; and

FIG. 27 is another schematic view illustrating a magnetic recordingmedium that can be used in this embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention will now be described with reference to thedrawings.

First Embodiment

A first embodiment of a microwave assisted magnetic head of theinvention is described in the case of recording on a multiparticlemedium for perpendicular magnetic recording.

FIG. 1 is a perspective view showing the schematic configuration of amagnetic recording head 5 according to the embodiment of the invention.

FIG. 2 is a perspective view showing a head slider on which the magneticrecording head 5 is mounted.

The magnetic recording head 5 of this embodiment comprises a reproducinghead section 70 and a writing head section 60. The reproducing headsection 70 comprises a magnetic shield layer 72 a, a magnetic shieldlayer 72 b, and a magnetic reproducing device 71 provided between themagnetic shield layer 72 a and the magnetic shield layer 72 b.

The writing head section 60 comprises a main magnetic pole 61, a returnpath (shield) 62, an excitation coil 63, and a spin torque oscillator10. The components of the reproducing head section 70 and the componentsof the writing head section 60 are separated from each other by aluminaor other insulators, not shown. The magnetic reproducing device 71 canbe a GMR device or a TMR (tunnel magnetoresistive effect) device. Inorder to enhance reproducing resolution, the magnetic reproducing device71 is placed between the two magnetic shield layers 72 a and 72 b.

The magnetic recording head 5 is mounted on a head slider 3 as shown inFIG. 2. The head slider 3, illustratively made of Al₂O₃/TiC, is designedand worked so that it can move relative to a magnetic recording medium(medium) 80 such as a magnetic disk while floating thereabove or beingin contact therewith. The head slider 3 has an air inflow side 3A and anair outflow side 3B, and the magnetic recording head 5 is disposedillustratively on the side surface of the air outflow side 3B.

The magnetic recording medium 80 has a medium substrate 82 and amagnetic recording layer 81 provided thereon. The magnetization of themagnetic recording layer 81 is controlled to a prescribed direction bythe magnetic field applied by the writing head section 60, and therebywriting is performed. The reproducing head section 70 reads thedirection of magnetization of the magnetic recording layer 81.

FIG. 3 is a schematic view illustrating the structure of the spin torqueoscillator 10 provided in this magnetic recording head 5.

The spin torque oscillator 10 has a structure in which a first electrode41, a spin injection layer 30 (second magnetic layer), an intermediatelayer 22 having high spin transmissivity, an oscillation layer 10 a(first magnetic layer), and a second electrode 42 are laminated in thisorder. By passing a driving electron flow 52 from this electrode 42 tothe electrode 41, a high-frequency magnetic field can be generated fromthe oscillation layer 10 a. The driving current density is preferablyfrom 5×10⁷ A/cm² to 1×10⁹ A/cm², and suitably adjusted so as to achievea desired oscillation. That is, the magnetic recording head 5 comprisesa laminated body including this spin injection layer 30, theintermediate layer 22 and the oscillation layer 10 a, and a pair ofelectrodes (electrode 41 and electrode 42) operable to pass a currentthrough this laminated body.

The electrode 41 and the electrode 42 can be made of a material havinglow electrical resistance and being resistant to oxidation such as Tiand Cu.

The intermediate layer 22 can be made of a material having high spintransmissivity such as Cu, Au, and Ag. The thickness of the intermediatelayer 22 is preferably from one atomic layer to 3 nm. This can reduceexchange coupling between the oscillation layer 10 a and the spininjection layer 30.

The oscillation layer 10 a is made of a high-Bs soft magnetic material(FeCo/NiFe laminated film) generating a magnetic field duringoscillation. The thickness of the oscillation layer 10 a is preferablyfrom 5 nm to 20 nm. The spin injection layer 30 is made of a CoPt alloywith its magnetization oriented perpendicular to the film plane. Thethickness of the spin injection layer 30 is preferably from 2 nm to 60nm.

The spin injection layer 30 and the oscillation layer 10 a can be a softmagnetic layer of CoFe, CoNiFe, NiFe, CoZrNb, FeN, FeSi, or FeAlSihaving a relatively high saturation magnetic flux density and havingmagnetic anisotropy in a direction longitudinal to the film plane, or aCoCr-based magnetic alloy film with its magnetization oriented in adirection longitudinal to the film plane. It is also possible tosuitably use a material layer having good perpendicular orientation suchas a CoCrPt, CoCrTa, CoCrTaPt, CoCrTaNb, or other CoCr-based magneticlayer, a TbFeCo or other RE-TM amorphous alloy magnetic layer, a Co/Pd,Co/Pt, CoCrTa/Pd, or other Co artificial lattice magnetic layer, aCoPt-based or FePt-based alloy magnetic layer, or a SmCo-based alloymagnetic layer, with the magnetization oriented perpendicular to thefilm plane. More than one of the above materials may be laminated. Thisis intended for adjusting the saturation magnetic flux density (Bs) andthe anisotropy magnetic field (Hk) of the oscillation layer 10 a and thespin injection layer 30.

The oscillation layer 10 a and the spin injection layer 30 made of theabove materials may be laminated via the intermediate layer 22 into alaminated ferri structure in which the above materials have antiparallelmagnetizations, or a structure in which the above materials haveparallel magnetizations. This is intended for increasing the oscillationfrequency of the oscillation layer 10 a, and for efficiently magnetizingthe spin injection layer 30. In this case, the intermediate layer 22 ispreferably made of a noble metal such as Cu, Pt, Au, Ag, Pd, or Ru, orcan be made of a nonmagnetic transition metal such as Cr, Rh, Mo, or W.

The magnetic field applied from the main magnetic pole 61 to the spintorque oscillator 10, the coercivity of the spin injection layer 30, andthe coercivity of the oscillation layer 10 a decrease in this order. Bycontrolling the magnetic field applied to the spin torque oscillator 10,the coercivity of the spin injection layer 30, and the coercivity of theoscillation layer 10 a in this manner, the magnetization direction ofthe spin injection layer 30 and the magnetization direction of theoscillation layer 10 a can always be kept parallel irrespective of thedirection of the writing magnetic field so that the oscillation layer 10a can oscillate stably.

By way of example, the magnetic field applied from the main magneticpole 61 to the spin torque oscillator 10 is 5 kOe to 10 kOe, whereas thecoercivity of the spin injection layer 30 can be set to e.g.approximately 3000 Oe, and the coercivity of the oscillation layer 10 acan be set to e.g. approximately 5 Oe.

As described later, to achieve stable oscillation driven by precessionabout the magnetization direction, the oscillation layer 10 a preferablyhas equal dimensions in the direction toward the adjacent track and inthe direction perpendicular to the air bearing surface (ABS) 100.

In FIG. 3, the lamination is made so that the oscillation layer 10 a isadjacent to the main magnetic pole 61. Alternatively, in order toefficiently apply a magnetic field from the main magnetic pole 61 to thespin injection layer 30, the lamination may be made so that the spininjection layer 30 is adjacent to the main magnetic pole 61.

In a writing head consisting only of the main magnetic pole 61, themagnetic field generated from the main magnetic pole 61 is generatedprimarily between the main magnetic pole 61 and the medium 80 and notsufficiently applied to the spin torque oscillator 10. Thus the magneticfield generated from the main magnetic pole 61 may be lower than thecoercivity of the spin injection layer 30. Hence it is preferable toprovide a shield 62 for absorbing the magnetic field generated from themain magnetic pole 61. That is, the shield 62 is preferably provided sothat the spin torque oscillator 10 is located between the main magneticpole 61 and the shield 62. In this case, the magnetic field from themain magnetic pole 61 efficiently flows into the shield 62, allowing themagnetic field to be sufficiently applied also to the spin injectionlayer 30. It is noted that the magnetic field applied to the spin torqueoscillator 10 can be optimized by adjusting the distance between themain magnetic pole 61 and the shield 62 and the shape of the mainmagnetic pole 61. For a large distance between the main magnetic pole 61and the shield 62, the magnetic field from the main magnetic pole 61 hasa perpendicular direction in the medium. However, decreasing thisdistance allows the magnetic field to be inclined from the perpendiculardirection in the medium. The inclined magnetic field has an advantagethat the magnetization of the medium can be reversed by a lower magneticfield.

Next, the operation of the microwave assisted magnetic head according tothe first embodiment of the invention is described.

FIG. 4 shows graphs illustrating the write operation of the magneticrecording head 5 provided with the spin torque oscillator 10 shown inFIG. 3. FIG. 4A shows the time dependence of the magnetic field appliedby the main magnetic pole 61 to the spin torque oscillator 10, FIG. 4Bshows the time dependence of the magnetization direction of the spininjection layer 30, FIG. 4C shows the time dependence of the oscillationfrequency of the oscillation layer 10 a of the spin torque oscillator10, and FIG. 4D shows the time dependence of the generated magneticfield strength. The oscillation frequency is proportional to thestrength of the static magnetic field applied to the oscillation layer10 a.

As shown in FIG. 4B, the magnetization direction of the spin injectionlayer 30 varies with the magnetic field from the main magnetic pole 61.Hence the spin injection layer 30 is magnetized at each writing time,avoiding demagnetization due to aging of the spin injection layer 30.Furthermore, the direction of the magnetic field applied by the mainmagnetic pole 61 to the spin torque oscillator 10, the magnetizationdirection of the oscillation layer 10 a, and the magnetization directionof the spin injection layer 30 are parallel irrespective of the writingdirection, and thus the oscillation condition does not depend on thewriting direction.

It is noted that, by applying an external DC magnetic field having anappropriate strength (1 kOe to 10 kOe) perpendicular to the air bearingsurface 100, the oscillation frequency and the oscillation strength ofthe spin torque oscillator 10 can be measured as a resistance changeproduced by the magnetoresistive effect of the spin torque oscillator10. As a result, the time dependence of the oscillation frequencysimilar to FIG. 4C and the time dependence of the oscillation strengthsimilar to FIG. 4D can be obtained.

Comparative Example

FIG. 5 shows graphs illustrating the write operation of a microwaveassisted magnetic head according to a comparative example. Morespecifically, FIG. 5A shows the time dependence of the magnetic fieldapplied by the main magnetic pole 61 to the spin torque oscillator 10,FIG. 5B shows the time dependence of the magnetization direction of thespin injection layer 30, FIG. 5C shows the time dependence of theoscillation frequency of the oscillation layer 10 a of the spin torqueoscillator 10, and FIG. 5D shows the time dependence of the generatedmagnetic field strength.

In this comparative example, as shown in FIG. 5B, the magnetization ofthe spin injection layer 30 is pinned irrespective of the writingdirection. Hence the direction of the magnetic field applied by the mainmagnetic pole 61 to the spin torque oscillator 10, the magnetizationdirection of the oscillation layer 10 a, and the magnetization directionof the spin injection layer 30 are parallel or antiparallel depending onthe writing direction. As a result, as shown in FIGS. 5C and 5D, theoscillation frequency and the generated magnetic field strength of thespin torque oscillator 10 vary with the writing direction.

The reason for the above-mentioned oscillation of the spin torqueoscillator 10 is described below in detail.

FIG. 6 is a conceptual view for illustrating the operation of themagnetic recording head 5 of this embodiment.

More specifically, FIG. 6 shows the situation where a magnetic field isgenerated in the positive direction from the main magnetic pole 61 tothe spin torque oscillator 10. The magnetic field from the main magneticpole 61 is higher than the coercivity of the spin injection layer 30.Hence the spin injection layer 30 is magnetized in the positivedirection. Consequently, the “sum of the magnetic field from the mainmagnetic pole 61 and the demagnetizing field of the spin injection layer30” in the oscillation layer 10 a is balanced with the spin torque fromthe spin injection layer 30 in the oscillation layer 10 a, resulting inoscillation of the oscillation layer 10 a. More specifically, among theelectrons that have passed through the oscillation layer 10 a from themain magnetic pole 61 side, the electrons with the same spin directionas the spin injection layer 30 pass through the spin injection layer 30,whereas the electrons with spin opposite to the spin injection layer 30are reflected at the interface between the intermediate layer 22 and thespin injection layer 30. Thus the electrons with spin opposite to thespin injection layer 30 flow into the oscillation layer 10 a. The spinangular momentum of these electrons is transferred to the magnetizationof the oscillation layer 10 a as a spin torque acting thereon, and thespin torque is directed opposite to the spin injection layer 30.Consequently, precession occurs in the oscillation layer 10 a, and itsmagnetization oscillates.

FIG. 7 is a conceptual view for illustrating the operation of themagnetic recording head 5 of this embodiment.

More specifically, FIG. 7 shows the situation where a magnetic field isgenerated in the negative direction from the main magnetic pole 61. Alsoin this case, like FIG. 6, the magnetic field from the main magneticpole 61 is higher than the coercivity of the spin injection layer 30.Hence the spin injection layer 30 is magnetized in the negativedirection. Consequently, the “sum of the magnetic field from the mainmagnetic pole 61 and the demagnetizing field of the spin injection layer30” in the oscillation layer 10 a is balanced with the spin torque fromthe spin injection layer 30 in the oscillation layer 10 a, resulting inoscillation of the oscillation layer 10 a. Also in this case, like FIG.6, the spin torque from the spin injection layer 30 acts on theoscillation layer 10 a, and its magnetization oscillates.

As described above, according to this embodiment, because themagnetization direction of the spin injection layer 30 and themagnetization direction of the oscillation layer 10 a are symmetric withrespect to the direction of the magnetic field from the main magneticpole 61, the oscillation frequency proportional to the magnetic fieldapplied to the oscillation layer 10 a, as well as the generated magneticfield, remains constant independent of the writing direction, achievingstable oscillation characteristics.

Furthermore, the spin injection layer 30 is magnetized at each writingtime by the magnetic field from the main magnetic pole 61. Thissignificantly decreases the demagnetization effect of the oscillationlayer 10 a due to aging and enables fabrication of a spin torqueoscillator 10 exhibiting stable oscillation. Hence this embodiment canbe used to provide a high-density magnetic recording apparatus havinghigh reliability.

In this embodiment, a high-frequency magnetic field can be generatedfrom the spin torque oscillator 10 by passing a driving electron flow 52from the oscillation layer 10 a side to the spin injection layer 30side.

FIGS. 8 and 9 are conceptual views for illustrating the operation ofpassing a driving electron flow 52 from the spin injection layer 30 sideto the oscillation layer 10 a side in the cases where the magnetic fieldfrom the main magnetic pole 61 to the spin torque oscillator 10 is inthe positive and negative direction, respectively. In these cases, thedirection of the spin torque from the spin injection layer 30 in theoscillation layer 10 a is the same as the magnetization direction of thespin injection layer 30. The direction of the spin torque is parallelto, and not balanced with, the “sum of the magnetic field from the mainmagnetic pole 61 and the demagnetizing field of the spin injection layer30”. Thus the magnetization of the oscillation layer 10 a does notundergo precession, and hence no oscillation occurs.

In magnetic recording to a medium 80 by the magnetic recording head 5,when the air bearing surface 100 of the magnetic recording head 5 isheld with a prescribed floating amount from the magnetic recording layer81 of the medium 80, the distance (magnetic spacing) between the airbearing surface 100 and the center of thickness of the magneticrecording layer 81 is kept at generally 10 nm, for example. The gapbetween the air bearing surface 100 and the surface of the magneticrecording layer 81 is generally 5 nm.

The spin torque oscillator 10 can be provided on either the trailingside or the leading side of the main magnetic pole 61. This is becausethe medium magnetization is not reversed by the recording magnetic fieldof the main magnetic pole 61 alone, but is reversed only in the regionwhere the high-frequency magnetic field of the spin torque oscillator 10is superposed on the recording magnetic field of the main magnetic pole61.

The oscillation layer 10 a may have a structure where the first magneticlayer, the intermediate layer, and the second magnetic layer arelaminated in this order. In this case, the first magnetic layer and thesecond magnetic layer form antiferromagnetic coupling or static magneticfield coupling, and oscillation occurs with the magnetizations thereofremaining antiparallel. This enables a longitudinal magnetic field to beefficiently applied to the medium 80. The intermediate layer ispreferably made of a noble metal such as Cu, Pt, Au, Ag, Pd, or Ru, andcan be made of a nonmagnetic transition metal such as Cr, Rh, Mo, or W.

Second Embodiment

Next, a second embodiment of the invention is described.

FIG. 10 is a perspective view showing the schematic configuration of amagnetic recording head 5 provided with a spin torque oscillator 10according to the second embodiment of the invention.

In this embodiment, a shield 62 is placed on the leading side of themain magnetic pole 61, and a laminated body of the spin torqueoscillator 10 is placed between the main magnetic pole 61 and the shield62. The surface of the main magnetic pole 61 and the shield 62 opposedto the laminated body is perpendicular to the lamination direction(thickness direction of the layer) of the laminated body. The spininjection layer 30 and the oscillation layer 10 a are magnetizedparallel to the lamination direction, i.e., in the direction from themain magnetic pole 61 to the shield 62 or in the opposite direction. Theoscillation layer 10 a includes a high-Bs soft magnetic material(FeCo/NiFe laminated film) generating a magnetic field duringoscillation. A bias layer 20 (fifth magnetic layer, in this case CoPtalloy layer) is provided between the main magnetic pole 61 and theoscillation layer 10 a to bias the high-Bs soft magnetic material layerby exchange coupling force.

The thickness of the high-Bs soft magnetic material is preferably from 5nm to 20 nm, and the thickness of the bias layer 20 is preferably from10 nm to 60 nm. The spin injection layer 30 is made of a CoPt alloy withits magnetization oriented perpendicular to the film plane. Thethickness of the spin injection layer 30 is preferably from 10 nm to 60nm. The thickness of the high-Bs soft magnetic material, the thicknessof the bias layer 20, and the thickness of the spin injection layer 30are suitably adjusted so as to achieve a desired oscillation.

The main magnetic pole 61 and the shield 62 also serve as electrodes forinjecting a driving electron flow 52 that drives the spin torqueoscillator 10. As a matter of course, back gap portions of the mainmagnetic pole 61 and the shield 62 are electrically insulated eachother. The driving current density is preferably from 5×10⁷ A/cm² to1×10⁹ A/cm², and suitably adjusted so as to achieve a desiredoscillation. In addition, in this embodiment, while the main magneticpole 61 and the shield 62 are directly adjacent to the laminated body, ametal body may be inserted between the main magnetic pole 61 or theshield 62 and the laminated body so as to adjust the distance from themain magnetic pole 61 and the shield 62 to the laminated body.

More specifically, the laminated body further includes the bias layer 20(fifth magnetic layer) provided between the electrode (in this case themain magnetic pole 61) at an opposite side of the oscillation layer 10 ato the intermediate layer 22 of electrodes and the oscillation layer 10a, having a coercivity lower than the magnetic field applied by the mainmagnetic pole 61.

Next, the operation of the magnetic recording head 5 of this embodimentis described.

The coercivity of the bias layer 20 and the coercivity of the spininjection layer 30 are lower than the magnetic field from the mainmagnetic pole 61. Hence, at the time of write operation, the bias layer20 and the spin injection layer 30 are magnetized in the same directionas the direction of the magnetic field from the main magnetic pole 61.Like the first embodiment, because the magnetization direction of thespin injection layer 30 and the magnetization direction of theoscillation layer 10 a are symmetric with respect to the direction ofthe magnetic field from the main magnetic pole 61, the oscillationcharacteristics do not depend on the polarity of the magnetic field fromthe main magnetic pole 61. Thus the principle of oscillation isdescribed illustratively in the case where the magnetic field from themain magnetic pole 61 is positive.

FIG. 11 is a conceptual view for illustrating the operation in the casewhere a magnetic field is generated in the positive direction from themain magnetic pole 61.

By the magnetic field from the main magnetic pole 61, the spin injectionlayer 30 and the bias layer 20 are magnetized in the positive direction.The magnetic field applied to the oscillation layer 10 a is composed ofthe “sum of the magnetic field from the main magnetic pole 61 and thedemagnetizing field of the spin injection layer 30” and the “exchangecoupling magnetic field from the bias layer 20”. The total of thesemagnetic fields is balanced with the spin torque from the spin injectionlayer 30, resulting in oscillation of the oscillation layer 10 a.

More specifically, among the electrons that have passed through theoscillation layer 10 a from the main magnetic pole 61 side, theelectrons having the same spin direction as the spin injection layer 30pass through the spin injection layer 30, whereas the electrons withspin opposite to the spin injection layer 30 are reflected at theinterface between the intermediate layer 22 and the spin injection layer30. Thus a spin torque from the spin injection layer 30 acts on theoscillation layer 10 a, where precession occurs and its magnetizationoscillates.

Furthermore, also in this embodiment, the spin injection layer 30 andthe bias layer 20 are magnetized at each writing time by the magneticfield from the main magnetic pole 61. This significantly decreases thedemagnetization effect of the oscillation layer 10 a due to aging andenables fabrication of a spin torque oscillator 10 exhibiting stableoscillation. Hence this embodiment can be used to provide a high-densitymagnetic recording apparatus having high reliability.

FIG. 12 shows graphs illustrating the write operation of the magneticrecording head 5 provided with the spin torque oscillator 10 shown inFIG. 11. More specifically, FIG. 12A shows the time dependence of themagnetic field applied by the main magnetic pole 61 to the spin torqueoscillator 10, FIG. 12B shows the time dependence of the magnetizationdirection of the spin injection layer 30, FIG. 12C shows the timedependence of the oscillation frequency of the oscillation layer 10 a ofthe spin torque oscillator 10, and FIG. 12D shows the time dependence ofthe generated magnetic field strength.

The oscillation frequency is proportional to the strength of themagnetic field applied to the oscillation layer 10 a. Hence, byproviding the oscillation layer 10 a with a bias layer 20, theoscillation layer 10 a can be operated at a higher frequency. As shownin FIG. 12C, the oscillation frequency of the spin torque oscillator 10reaches 30 GHz.

To achieve ultrahigh-density recording, it is essential to preventthermal fluctuations of the medium. This requires the enhancement of themedium coercivity (Hc), which simultaneously results in increasing theresonance frequency of the medium and increasing the oscillationfrequency required for the spin torque oscillator 10. In contrast,combination with the spin torque oscillator 10 having a structure asshown in FIG. 11 enables writing also to a high-Hc medium capable ofultrahigh-density recording.

It is noted that, to optimize the oscillation frequency, a nonmagneticlayer may be interposed between the bias layer 20 and the oscillationlayer 10 a. The nonmagnetic layer is preferably made of a noble metalsuch as Cu, Pt, Au, Ag, Pd, or Ru, or can be made of a nonmagnetictransition metal such as Cr, Rh, Mo, or W.

Furthermore, the materials and the lamination films thereof describedabove with reference to the first embodiment can be also used for thespin injection layer 30 and the oscillation layer 10 a to achieve asimilar effect.

Third Embodiment

Next, a third embodiment of the invention is described.

FIG. 13 is a perspective view showing the schematic configuration of amagnetic recording head 5 provided with a spin torque oscillator 10according to the third embodiment of the invention.

In this embodiment, a shield 62 is placed on the trailing side of themain magnetic pole 61, and the spin torque oscillator 10 is providedbetween the main magnetic pole 61 and the shield 62. The surface of themain magnetic pole 61 and the shield 62 opposed to the laminated body isparallel to the lamination direction (thickness direction of the layer)of the spin torque oscillator 10. The spin injection layer 30 and theoscillation layer 10 a are magnetized perpendicular to the laminationdirection, i.e., in the direction from the main magnetic pole 61 to theshield 62 or in the opposite direction. Although the electrodes of thespin torque oscillator 10 are not shown in FIG. 13, electrodes capableof passing a current parallel to the lamination direction of the spininjection layer 30, the intermediate layer 22, and the oscillation layer10 a are connected to the spin torque oscillator 10. Furthermore, thespin torque oscillator 10 is insulated from the main magnetic pole 61and the shield 62. Hence, at the time of write operation, the effect ofeddy current generated from the main magnetic pole 61 can be prevented.The lamination direction of the spin torque oscillator 10 isperpendicular to the medium moving direction 85 in the example shown inFIG. 13, however, the invention is not limited to this specific example.The lamination direction of the spin torque oscillator 10 can beparallel to the medium moving direction 85.

A magnetic flux focusing layer 40 a (third magnetic layer) is providedbetween the spin torque oscillator 10 and the main magnetic pole 61. Themagnetic flux focusing layer 40 a can be made of a soft magneticmaterial such as CoFe, CoNiFe, NiFe, CoZrNb, FeN, FeSi, or FeAlSi havinga relatively high saturation magnetic flux density and having magneticanisotropy in a direction longitudinal to the film plane. Furthermore, amagnetic flux focusing layer 40 b (fourth magnetic layer) is providedbetween the spin torque oscillator 10 and the shield 62. The magneticflux focusing layer 40 b can be made of a soft magnetic material such asCoFe, CoNiFe, NiFe, CoZrNb, FeN, FeSi, or FeAlSi having a relativelyhigh saturation magnetic flux density and having magnetic anisotropy ina direction longitudinal to the film plane.

With the increase of frequency, the distance from the magnetic recordingmedium 80 to the main magnetic pole 61 and the shield 62 decreases.Hence the magnetic field generated from the main magnetic pole 61 tendsto be directed toward the magnetic recording medium 80. Thus themagnetic flux focusing layers 40 a and 40 b, being soft magnetic, areprovided to focus the magnetic field from the main magnetic pole 61 onthe spin torque oscillator 10. The magnetic flux focusing layers 40 aand 40 b serve to guide the magnetic field generated from the mainmagnetic pole 61 toward the spin torque oscillator 10.

Let Bsa and Bsb be the saturation magnetic flux density in the magneticflux focusing layers 40 a and 40 b, and Ωa and Ωb the solid angle of themagnetic flux focusing layers 40 a and 40 b subtended by the spin torqueoscillator 10. When the magnetic flux focusing layers are saturated, themagnetic field applied to the spin torque oscillator 10 is given by:

H=Bsa×Ωa+Bsb×Ωb  (1)

Hence, to efficiently apply a magnetic field to the spin torqueoscillator 10, it is preferable to increase the saturation magnetization(Ms) of the magnetic flux focusing layers as much as possible. Inaddition, the solid angle Ω of the magnetic flux focusing layer may beincreased by narrowing the distance between the main magnetic pole 61and the shield 62 and/or increasing the dimensions of the magnetic fluxfocusing layers 40 a and 40 b.

Furthermore, to efficiently focus the magnetic flux on the spin torqueoscillator 10, the main magnetic pole 61 may be laminated with themagnetic flux focusing layer 40 a, and/or the shield 62 may be laminatedwith the magnetic flux focusing layer 40 b. On the other hand, toefficiently apply the magnetic field from the main magnetic pole 61 tothe medium, a nonmagnetic material, i.e., a nonmagnetic metal or aninsulator, may be laminated between the main magnetic pole 61 and themagnetic flux focusing layer 40 a, or between the shield 62 and themagnetic flux focusing layer 40 b.

Next, the operation of the magnetic recording head 5 according to thisembodiment is described.

The coercivity of the spin injection layer 30 is lower than the magneticfield from the main magnetic pole 61. Hence, at the time of writeoperation, the spin injection layer 30 is magnetized in the samedirection as the direction of the magnetic field from the main magneticpole 61. Like the first embodiment, because the magnetization directionof the spin injection layer 30 and the magnetization direction of theoscillation layer 10 a are symmetric with respect to the direction ofthe magnetic field from the main magnetic pole 61, the oscillationcharacteristics do not depend on the polarity of the magnetic field fromthe main magnetic pole 61. Thus the principle of oscillation isdescribed illustratively in the case where the magnetic field from themain magnetic pole 61 is positive.

FIG. 14 is a conceptual view for illustrating the operation in the casewhere a magnetic field is generated in the positive direction from themain magnetic pole 61 toward the spin torque oscillator 10.

By the magnetic field from the main magnetic pole 61, the spin injectionlayer 30 is magnetized in the positive direction. The magnetic fieldapplied to the oscillation layer 10 a is composed of the “sum of themagnetic field from the main magnetic pole 61 and the magnetic fieldfrom the magnetic flux focusing layer”. This magnetic field is balancedwith the spin torque from the spin injection layer 30, resulting inoscillation of the oscillation layer 10 a.

More specifically, among the electrons that have passed through theoscillation layer 10 a, the electrons having the same spin direction asthe spin injection layer 30 pass through the spin injection layer 30,whereas the electrons with spin opposite to the spin injection layer 30are reflected at the interface between the intermediate layer 22 and thespin injection layer 30. Thus a spin torque from the spin injectionlayer 30 acts on the oscillation layer 10 a, where precession occurs,resulting in oscillation.

Furthermore, the spin injection layer 30 is magnetized at each writingtime by the magnetic field from the main magnetic pole 61. Thissignificantly decreases the demagnetization effect of the oscillationlayer 10 a due to aging and enables fabrication of a spin torqueoscillator 10 exhibiting stable oscillation. Hence this embodiment canbe used to provide a high-density magnetic recording apparatus havinghigh reliability.

Furthermore, to achieve stable oscillation, the oscillation layer 10 apreferably has equal dimensions in the direction perpendicular to theair bearing surface (ABS) 100 and in its lamination direction.

To obtain a suitable oscillation frequency, the oscillation layer 10 amay be made of the materials and the laminated films thereof describedin the first embodiment. To adapt the coercivity of the spin injectionlayer 30 to the strength of the magnetic field from the main magneticpole 61, the spin injection layer 30 may be made of the materials andthe laminated films thereof described in the first embodiment.

To increase the frequency, a bias layer 20 may be provided adjacent tothe oscillation layer 10 a as in the second embodiment of the invention.

The remaining head configuration, the operating principle, and theeffect in this embodiment are the same as those described in the firstembodiment.

Each magnetic layer of the spin torque oscillator 10 may have an easymagnetization axis in the lamination direction in the case of FIG. 10and in the in-plane direction in the case of FIG. 13. The easy axis canbe fixed by growing a crystal so that, for a CoPt-based material, forexample, the c-axis is directed along the easy axis.

Fourth Embodiment

Next, a fourth embodiment of the invention is described.

FIG. 15 is a perspective view showing the schematic configuration of amagnetic recording head 5 according to the fourth embodiment of theinvention.

As shown in FIG. 15, the magnetic recording head 5 according to thefourth embodiment of the invention is provided with the shield 62 placedon the trailing side of the main magnetic pole 61, and the laminatedbody of the spin torque oscillator 10 is provided between the mainmagnetic pole 61 and the shield 62. The direction from the main magneticpole 61 to the shield 62 is substantially parallel to the laminationdirection (thickness direction of the layer) of the spin torqueoscillator 10. The spin injection layer 30 and the oscillation layer 10a are magnetized substantially parallel to the lamination direction,i.e., in the direction from the main magnetic pole 61 to the shield 62or in the opposite direction.

It is noted that, in the magnetic recording head 5 according to thisembodiment, the shield 62 serves as the electrode 41 on the spininjection layer 30 side and the main magnetic pole 61 serves as theelectrode 42 on the oscillation layer 10 a side. That is to say, a pairof electrodes are illustratively the main magnetic pole 61 and theshield 62. As a matter of course, back gap portions of the main magneticpole 61 and the shield 62 are electrically insulated each other. Inaddition, in this embodiment, while the main magnetic pole 61 and theshield 62 are directly adjacent to the laminated body, a metal body maybe inserted between the main magnetic pole 61 or the shield 62 and thelaminated body so as to adjust the distance from the main magnetic pole61 and the shield 62 to the laminated body.

The oscillation layer 10 a can be made of, for example, a laminated bodyof CoFe with a thickness of 10 Å and NiFe with a thickness of 60 Å. Theintermediate layer 22 can be based on, for example, Cu with a thicknessof 20 Å. Furthermore, the injection layer 30 and the bias layer 20 canbe made of, for example, a CoCr alloy with a thickness of 400 Å addedwith Os of 5 at %.

It is noted that the oscillation layer 10 a and the intermediate layer22 can be made of materials described with reference to the firstembodiment and materials having a laminated structure.

Furthermore, the spin injection layer 30 and the bias layer 20 may beillustratively made of a Co-based hard magnetic alloy such as a CoPtalloy or the like other than a CoCr alloy. More specifically, the spininjection layer 30 and the bias layer 20 can be made of a variety ofmaterials having magnetization in a perpendicular direction.Furthermore, an additional element for a variety of materials having themagnetization in the perpendicular direction such as a Co-based hardmagnetic alloy or the like may be made of an element such as Ru, W, Re,Ir, Sm, Eu, Tb, Gd, Dy, Ho, Rh, Pd other than Os. More specifically, atleast any of the spin injection layer 30 and the bias layer 20 cancontain at least one selected from a group comprising of Ru, W, Re, Os,Ir, Sm, Eu, Tb, Gd, Dy, Ho, Rh and Pd.

These elements strengthen s-d interaction or spin-orbit interaction,therefore a damping constant can be increased from normal 0.02 to0.05˜0.5.

FIG. 16 is a graph illustrating the relation between a magnetizationinversion time and a damping constant in a magnetic recording headaccording to the fourth embodiment of the invention.

More specifically, FIG. 16 shows the relation between the magnetizationinversion time of the spin injection layer 30 or the bias layer 20 andthe damping constant, when the direction of the magnetic field from themain magnetic pole 61 to the spin torque oscillator 10 changes from thepositive direction to the negative direction.

The magnetization inversion time refers to time for the inversion of themagnetization of the spin injection layer 30 from the positive directionto the negative direction, when the applied magnetic field from the mainmagnetic pole 61 to the spin injection layer 30 inverts instantaneouslyfrom +5 kOe to −60 kOe.

The normal damping constant of the spin injection layer 30 or the biaslayer 20 is about 0.02, and the magnetization inversion time is 0.64 nsas shown in FIG. 16. On the other hand, the time for the inversion ofthe magnetic field from the main magnetic pole 61 from the positivedirection to the negative direction is 0.3 ns. That is, themagnetization inversion time in this case is about two times of the timefor the inversion of the magnetic field, thus at the inversion of themagnetic field from the main magnetic pole 61, the magnetizationinversion of the spin injection layer 30 and the bias layer 20 lagsbehind to cause the oscillation to be unstable. As a result, recordingof 0/1 on the medium in a magnetization inversion region, particularlysatisfactory characteristics of overwriting is difficult to be realized.

On the other hand, in the magnetic recording head 5 according to thisembodiment, the damping constant of the spin injection layer 30 and thebias layer 20 is 0.1, and as shown in FIG. 16, the magnetizationinversion time is to be 0.29 ns. The time for inverting the magneticfield from the magnetic main pole 61 from the positive direction to thenegative direction is 0.3 ns, and is substantially equivalent to themagnetization inversion time. Therefore, the magnetization of the spininjection layer 30 and the bias layer 20 inverts at the substantiallysame speed as the inversion speed of the magnetic field from the mainmagnetic pole 61. As a result, the magnetic recording head 5 accordingto this embodiment enables break of radio frequency magnetic fieldgeneration to minimize at inversion of the magnetic field from themagnetic main pole 61, allowing a stable magnetic recording.

Furthermore, the increase of the damping constant of the spin injectionlayer 30 and the bias layer 20 allows magnetic recording to medium to beperformed more effectively through improvement of oscillation efficiencyof the oscillation layer 10 a. This will now be described.

The critical driving current density Jc at which the magnetic layerstarts to oscillate by spin torque can be expressed by a followingformula:

$\begin{matrix}{J_{c} = {\left( {H_{ext} + {Hk} - {BsNd}} \right)\frac{\alpha \; {eMs}\; \delta}{p_{o}\hslash}}} & (2)\end{matrix}$

where Hext is the sum of exchange coupling magnetic field from theexternal magnetic field and the adjacent magnetic material, Hk is theanisotropic magnetic field, Bs is the saturated magnetic flux density(that is, 4 nMs), Nd is the demagnetization field constant, α is thedamping constant, e is the elementary electric charge, δ is the filmthickness, po is the porality, and h is the Planck constant.

Since the critical driving current density Jc is proportional to thedamping constant as shown in formulae 2, the critical driving currentdensity Jc of the spin injection layer 30 increases due to the increaseof the damping constant of the spin injection layer 30 and the spininjection layer 30 becomes to be hard to rotate. As a result, effectiveinjection of the energy of spin torque to the oscillation layer 10 abecomes possible. Furthermore, the driving current density and Msδ ofthe oscillation layer 10 a may be increased in proportion to theincrease of the critical driving current density Jc of the spininjection layer 30. At this time, since the Msδ of the oscillation layer10 a is proportiona to the radio frequency magnetic field strength, theradio frequency magnetic field strength to the medium increases. Theradio frequency magnetic field strength needs about 10% of Hk of themedium, the increase of the radio frequency magnetic field strengthallows higher Hk medium, that is, higher Ku medium to be recorded, andfurther higher density recording can be achieved.

Furthermore, since the oscillation layer 10 a and the bias layer 20 aredirectly laminated, a part of magnetization at the interface of the biaslayer 20 oscillates under influence of the oscillation of theoscillation layer 10 a via the exchange coupling force and thesubstantial exchange coupling magnetic field from the bias layer 20 tothe oscillation layer 10 a. Here, by increasing the damping constant ofthe bias layer 20, oscillation becomes to be hard at the interface ofthe bias layer 20, and the exchange coupling magnetic field from thebias layer 20 to the oscillation layer 10 a allowed to be substantiallyincreased. As the exchange coupling magnetic field increases, theoscillation frequency also increases. Furthermore, in microwave assistedmagnetic recording, it is necessary to coincide the oscillationfrequency with the resonance frequency of the medium. Since the resonantfrequency of magnetic material is proportional to the anisotropicmagnetic field (Hk) strength, the increase of the oscillation frequencyof the oscillation layer 10 a allows a higher Hk medium, that is, a highKu medium to be used. As a result, further high density recording can beachieved.

It is noted that for optimizing the oscillation characteristics and thecritical driving current density Jc of the bias layer 20 and the spininjection layer 30, additive elements (Ru, W, Re, Os, Ir, Sm, Eu, Tb,Gd, Dy, Ho, Rh, Pd or the like) to the bias layer 20 and the spininjection layer 30 and the amount of additive may be different,respectively.

Fifth Embodiment

Next, a fifth embodiment of the invention will be described.

FIG. 17 is a perspective view illustrating the schematic configurationof a magnetic recording head 5 according to the fifth embodiment of theinvention.

As shown in FIG. 17, the magnetic recording head 5 according to thefifth embodiment of the invention is provided with the shield 62 placedon the trailing side of the main magnetic pole 61, and the spin torqueoscillator 10 is provided between the main magnetic pole 61 and theshield 62. The direction from the main magnetic pole 61 to the shield 62is substantially perpendicular to the lamination direction (thicknessdirection of the layer) of the spin torque oscillator 10. The spininjection layer 30 and the oscillation layer 10 a are magnetizedsubstantially perpendicular to the lamination direction, i.e., in thedirection from the main magnetic pole 61 to the shield 62 or in theopposite direction.

It is noted that the electrode 41 on the spin injection layer 30 sideand the electrode 42 on the oscillation layer 10 a side are abbreviated.

The oscillation layer 10 a can be made of, for example, a laminated bodyof CoFe with a thickness of 10 Å and NiFe with a thickness of 60 Å. Theintermediate layer 22 can be based on, for example, Cu with a thicknessof 20 Å. Furthermore, the injection layer 30 can be made of, forexample, a CoCr alloy with a thickness of 400 Å. The electrode 41adjacent to the spin injection layer 30 can be made of, for example, alaminated body of Pt with a thickness of 40 Å and Ru with a thickness of40 Å.

The electrode 41 adjacent to the spin injection layer 30 may be made ofa material containing at least one selected from a group comprising ofRu, Rh, Pd, Ir and Pt having a short spin scattering distance.Furthermore, the electrode 41 may be made of a material containing analloy comprising of at least two selected from a group comprising of Ru,Rh, Ir and Pt.

The electrode 41 may be made of a laminated film of a layer containingat least one selected from a group comprising of Cu, Au, Ag and Alhaving a long spin scattering distance and a layer containing at leastone elected from a group comprising of Ru, Rh, Pd, Ir, Pt having a shortspin scattering distance.

Furthermore, the electrode 41 may be made of a laminated film of a layercontaining at least one selected from a group comprising of Cu, Au, Agand Al having a long spin scattering distance, and an alloy containingat least two selected from a group comprising of Ru, Rh, Pd, Ir, Pthaving a short spin scattering distance.

Furthermore, the electrode 41 may be made of a laminated film of analloy containing at least two selected from a group comprising of Cu,Au, Ag and Al having a long spin scattering distance, and a filmcontaining at least one selected from a group comprising of Ru, Rh, Pd,Ir, Pt having a short spin scattering distance.

Furthermore, the electrode 41 may be made of a laminated film of analloy containing at least two selected from a group comprising of Cu,Au, Ag and Al having a long spin scattering distance, and an alloycontaining at least two selected from a group comprising of Ru, Rh, Pd,Ir, Pt having a short spin scattering distance.

Use of above materials as materials for electrode 41 enables the dampingconstant of the spin injection layer 30 to increase. This allows astable magnetic recording to be realized and a further high densityrecording to be performed by increasing the damping constant of the spininjection layer 30 as described in the fourth embodiment of theinvention.

FIG. 18 is a conceptual view illustrating a characteristic of spintorque in the magnetic recording head 5 according to the fifthembodiment of the invention.

More specifically, FIG. 18 is the conceptual view for illustrating areason why using materials having a short spin scattering distance forthe electrode 41 on the spin injection layer 30 side enables the dampingconstant of the spin injection layer 30 to increase.

As shown in FIG. 18, when the magnetization rotates due to fluctuationof the magnetization of the spin injection layer 30, a spin flow 31flows into the electrode 41 from the spin injection layer 30. The spinflow 31 gets angular momentum from the magnetization of the spininjection layer 30. Since the spin scattering distance of the electrode41 is short, the spin flow arriving at the electrode 41 is completelyabsorbed in the vicinity of the interface with the spin injection layer30, little flow returns from the electrode 41 to the spin injectionlayer 30. Thus, almost all angular momentum of the spin flow 31 isscattered at the electrode 41. More specifically, this is equivalent tothat the spin torque 32 is applied from the electrode 41 in a directionlowering the rotation, when the electrode 41 made of materials having ashort spin scattering distance is adjacent to the spin injection layer30 with rotating magnetization, and corresponds to the effectiveincrease of the damping constant.

It is noted that the damping constant decreases similarly in a laminatedfilm which the spin injection layer 30, materials having a long spinscattering distance and materials having a short spin scatteringdistance are laminated in this order, and a thickness of the materialshaving a long spin scattering distance is less than the spin scatteringdistance. It is for this reason that the spin flow generated in the spininjection layer 30 arrives at materials having a short spin scatteringdistance without disturbance during passing through materials having along spin scattering distance.

When the bias layer 20 is provided, the electrode 42 adjacent to thebias layer 20 may be made of a material containing at least one selectedfrom a group comprising of Ru, Rh, Pd, Ir and Pt having a short spinscattering distance, further more, electrode 42 adjacent to the biaslayer 20 may be made of an alloy containing at least two selected from agroup comprising of Ru, Rh, Pd, Ir and Pt.

Alike the electrode 41 described above, the electrode 42 may be made ofa laminated film of a film containing at least one selected from a groupcomprising of Cu, Au, Ag and Al having a long spin scattering distanceor an alloy containing at least two selected from the group, and a filmcontaining at least one selected from a group comprising of Ru, Rh, Pd,Ir, Pt having a short spin scattering distance or an alloy containing atleast two selected from the group.

Use of above materials as materials for electrode 41 enables the dampingconstant of the bias layer 20 to increase. The reason why the dampingconstant is allowed to be increased is the same reason why the dampingconstant of the spin injection layer 30 described above is increased.Increase of the damping constant of the bias layer 20 using theelectrode material like this enables the magnetic recording head 5according to this embodiment to perform a further high density recordingalike the fourth embodiment.

It is noted that the electrode 42 may contain at least one selected froma group comprising of Ru, Rh, Pd, Ir and Pt also when the bias layer 20is not provided.

Furthermore, both the electrode 41 and the electrode 42 may contain atleast one selected from a group comprising of Ru, Rh, Pd, Ir and Pt.

Furthermore, at least any one of the spin injection layer 30 and thebias layer 20 may contain at least one selected from a group comprisingof Ru, W, Re, Os, Ir, Eu, Tb, Gd, Dy, Ho, Rh and Pd as described in thefourth embodiment, and at least any one of the electrode 41 and theelectrode 42 may simultaneously contain at least one selected from agroup comprising of Ru, Rh, Pd, Ir and Pt.

Sixth Embodiment

Next, a sixth embodiment of the invention will be described.

FIG. 19 is a perspective view illustrating the schematic configurationof a magnetic recording head 5 according to the sixth embodiment of theinvention.

As shown in FIG. 19, the magnetic recording head 5 according to thesixth embodiment of the invention is provided with the shield 62 placedon the trailing side of the main magnetic pole 61, and the laminatedbody of the spin torque oscillator 10 is provided between the mainmagnetic pole 61 and the shield 62. The direction from the main magneticpole 61 to the shield 62 is substantially parallel to the laminationdirection (thickness direction of the layer) of the spin torqueoscillator 10. The spin injection layer 30 and the oscillation layer 10a are magnetized substantially parallel to the lamination direction,i.e., in the direction from the main magnetic pole 61 to the shield 62or in the opposite direction.

A second bias layer (sixth magnetic layer) 91 adjacent to the spininjection layer 30 and a third bias layer (seventh magnetic layer) 92adjacent to the bias layer 20 are further provided. These second biaslayer 91 and the third bias layer 92 are magnetized substantiallyparallel to the lamination direction of the spin torque oscillator 10,i.e., in the direction from the main magnetic pole 61 to the shield 62or in the opposite direction slightly slanted perpendicularly to thelamination direction.

More specifically, an easy magnetization axis of the second bias layer(sixth magnetic layer) 91 is substantially perpendicular to a normalline of the surface of the main magnetic pole 61 opposed to thelaminated body. An easy magnetization axis of the third bias layer(seventh magnetic layer) 92 is also substantially perpendicular to anormal line of the surface of the main magnetic pole 61 opposed to thelaminated body.

Furthermore, an absolute value of the crystalline anisotropy magneticfield of the second bias layer (sixth magnetic layer) 91 is more than orequal to ½ of the saturation flux density of the second bias layer(sixth magnetic layer) 91. An absolute value of the crystallineanisotropy magnetic field of the third bias layer (seventh magneticlayer) 92 is more than or equal to ½ of the saturation flux density ofthe third bias layer (seventh magnetic layer) 92.

It is noted that in the magnetic recording head 5 according to thisembodiment the shield 62 serves as the electrode 41 on the spininjection layer 30 side, and the main magnetic pole 61 serves as theelectrode 42 on the oscillation layer 10 a side. That is, this is thecase that a pair of electrodes are the main magnetic pole 61 and theshield 62. The back gap portions of the main magnetic pole 61 and theshield 62 are naturally electrically insulated each other. While in thisembodiment, the main magnetic pole 61 and the shield 62 are directlyadjacent to the laminated body, a metal body may be inserted between themain magnetic pole 62 and the shield 62 and the laminated body in orderto adjust the distance between the main magnetic pole 61 and the shield62 and the laminated body.

A size of the spin torque oscillator in the vertical direction to thecurrent direction is, for example, a square of 600 Å edges. The thirdbias layer 92 adjacent to the bias layer 20 can be made of, for example,CoIr with a film thickness of 100 Å. The bias layer 20 can be made of,for example, a CoCr alloy with a film thickness of 400 Å. Theoscillating layer 10 a can be made of, for example, a laminated body ofFeCo with a film thickness of 30 Å, NiFe with a film thickness of 30 Å,FeCo with a film thickness of 30 Å and NiFe with a film thickness of 30Å laminated in this order. The intermediate layer can be made of, forexample, Cu with a film thickness of 30 Å. The spin injection layer 30can be made of, for example, a CoPt alloy with a film thickness of 200Å. The second bias layer 91 adjacent to the spin injection layer 30 canbe made of, for example, FeCo with a film thickness of 50 Å.

It is noted that the oscillating layer 10 a and the intermediate layer22 can be based on the materials and the laminated structure describedin the first embodiment.

Furthermore, the bias layer 20 and the spin injection layer 30 may bemade of a Co-based hard magnetic alloy such as CoCr alloy or the like.In order to set the bias layer 20 and the spin injection layer 30 to bea single magnetic domain or to be within a recording gap, these filmthicknesses may be adjusted suitably between 100 Å and 800 Å.

In addition, the additive elements described in the fourth embodimentmay be added to the spin injection layer 30.

The second bias layer 91 and the third bias layer 92 can be based on thehigh-Bs soft magnetic materials described in the first embodiment andmaterials having a negative uniaxial crystalline anisotropy such as CoIror the like and a laminated structure of them. When materials of thesecond bias layer 91 and the third bias layer 92 or the laminatedstructure are changed, the saturation flux densities and the crystallineanisotropy magnetic fields of the second bias layer 91 and the thirdbias layer 92 can be adjusted and the magnetization inversion time canbe adjusted.

FIG. 20 is a graph illustrating a characteristic of the magneticrecording head 5 according to the sixth embodiment of the invention.

More specifically, FIG. 20 shows the relationship between the saturationflux density of the second bias layer 91 adjacent to the spin injectionlayer 30 and the magnetization inversion time of the spin injectionlayer 30.

In figure the same, by taking the second bias layer 91 as a laminatedbody of NiFe and FeCo and changing a film thickness ratio of NiFe andFeCo, the saturation flux density of the second bias layer 91 is changedfrom 800 emu/cc to 1950 emu/cc. The magnetization inversion time isdefined in the same way as described in the fourth embodiment.

As shown in FIG. 20, when the second bias layer 91 (longitudinal biaslayer) is not provided, the magnetization inversion time is 0.65 ns, butlaminating the second bias layer 91 (longitudinal bias layer) on thespin injection layer 30 shortens the magnetization inversion time to0.56˜0.29 ns.

In this way, shortening of the magnetization inversion time enablesbreak of radio frequency magnetic field generation to minimize atinversion of the magnetic field from the magnetic main pole, allowing astable magnetic recording. Particularly the higher the saturation fluxdensity of the second bias layer 91, the shorter the magnetizationinversion time becomes. This is the reason why with the increase of thesaturation flux density of the second bias layer 91 influence of theshape anisotropy becomes larger, and the longitudinal magnetizationcomponent of the second bias layer 91 becomes larger. Through theexchange-coupling force a longitudinal torque proportional to thelongitudinal magnetization component of the second bias layer 91 isapplied to the spin injection layer 30, the larger the torque, a highspeed magnetization inversion becomes possible.

It is noted that the characteristic of the second bias layer 91 adjacentto the spin injection layer described above can also be applied to thethird bias layer 92 adjacent to the bias layer 20.

On the other hand, when the exchange coupling force between the spininjection layer 30 and the second bias layer 91 is too strong, thesecond bias layer 91 may be magnetized perpendicularly due to theperpendicular torque from the spin injection layer. In this case, sincethere is no longitudinal magnetization component in the second biaslayer 91, no longitudinal torque component is applied to the spininjection layer 30, and the magnetization inversion time becomesimpossible to be reduced. In order to avoid the situation like this, theexchange coupling force between the spin injection layer 30 and thesecond bias layer 91 may be adjusted by inserting a nonmagnetic layerbut not laminating directly the spin injection layer 30 and the secondbias layer 91.

The exchange coupling force between these layers may be adjusted byinserting a nonmagnetic layer similarly between the bias layer 20 andthe third bias layer 92 adjacent to the bias layer 20.

Furthermore, an overshoot current may be passed through a magnetic mainpole coil at the magnetization inversion. The overshoot current enablesthe magnetization inversion time to reduce. This is the reason why theovershoot current increases the magnetic field and the torque from themain magnetic pole 61 to the spin torque oscillator 10. A magnitude ofthe overshoot current, a rise time, a holding time and a fall time maybe adjusted so that a bit error code of recording is optimized.

Furthermore, in order to invert early an oscillating state of theoscillation layer 10 a, a current pulse may be superposed on a drivingcurrent at the magnetization inversion. An oscillation direction of theoscillation layer 10 a is also inverted at the magnetization inversioncorresponding to the magnetization inversion of the bias layer 20 andthe spin injection layer 30. Superposing the pulse current on thedriving current increases the spin torque to the oscillation layer 10 aby the pulse current. Consequently, the oscillation direction of theoscillation layer 10 a is allowed to invert in quick response to themagnetization inversion of the bias layer 20 and the spin injectionlayer 30. Strength of the pulse current, a rise time, a holding time, afall time and procrastination and delay of pulse start timing to themagnetization inversion may be adjusted so that overwriting of recordingand a bit error rate is optimized.

It is noted that the magnetic recording head 5 according to thisembodiment described above is provided with both the second bias layer91 adjacent to the spin injection layer 30 and the third bias layer 92adjacent to the bias layer 20, however the invention is not limited tothis, any one of the second bias layer 91 adjacent to the spin injectionlayer 30 and the third bias layer 92 adjacent to the bias layer 20 maybe provided. This can reduce the magnetization inversion time andenables a stable magnetic recording.

Seventh Embodiment

Next, a seventh embodiment of the invention will be described.

FIG. 21 is a perspective view illustrating the schematic configurationof a magnetic recording head 5 according to the seventh embodiment ofthe invention.

As shown in FIG. 21, the magnetic recording head 5 according to theseventh embodiment of the invention is provided with the shield 62placed on the trailing side of the main magnetic pole 61, and thelaminated body of the spin torque oscillator 10 is provided between themain magnetic pole 61 and the shield 62. The direction from the mainmagnetic pole 61 to the shield 62 is substantially parallel to thelamination direction (thickness direction of the layer) of the spintorque oscillator 10. The spin injection layer 30 and the oscillationlayer 10 a are magnetized substantially parallel to the laminationdirection, i.e., in the direction from the main magnetic pole 61 to theshield 62 or in the opposite direction.

The second bias layer (sixth magnetic layer) 91 adjacent to the spininjection layer 30 is provided. The second bias layer 91 is magnetizedsubstantially parallel to the lamination direction from the mainmagnetic pole 61 to the shield 62 or in the opposite direction slightlyslanted perpendicularly to the lamination direction.

The oscillation layer 10 a of the spin torque oscillator 10 can be madeof, for example, a laminated body of FeCo with a film thickness of 30 Åand CoFeB with a thickness of 90 Å. The intermediate layer 22 can bemade of, for example, Cu with a film thickness of 30 Å. The spininjection layer 30 can be made of, for example, CoPt alloy with athickness of 200 Å.

Furthermore, the second bias layer 91 adjacent to the spin injectionlayer 30 can be made of, for example, CoIr with a film thickness of 100Å.

Furthermore, a laminated structure body 25 of Ta with a film thicknessof 30 Å, Ru with a film thickness of 30 Å, and Cu with a film thicknessof 30 Å is provided between the oscillation layer 10 a and the mainmagnetic pole 61. The laminates structure body 25 and the main magneticpole 61 serve as the electrode 42 on the oscillation layer 10 a side andthe shield 62 serves as the electrode 41 on the spin injection layer 30side. The back gap portions of the main magnetic pole 61 and the shield62 are electrically insulated each other. The laminated structure body25 allows a distance between the main magnetic pole 61 and theoscillation layer 10 a to be adjusted, and a recording magnetic field tobe superposed effectively on a radio frequency magnetic field on themedium.

A metal body may be inserted between the spin injection layer 30 and theshield depending on the film thicknesses of the oscillation layer 10 aand the spin injection layer 30.

It is noted that the oscillation layer 10 a and the intermediate layer22 can be based on the material and the structure described in the firstembodiment.

Furthermore, the spin injection layer 30 can be made of Co-based hardmagnetic alloy such as CoCr or the like. The film thickness of the spininjection layer 30 may be adjusted suitably between 100 Å and 800 Å.

In addition, the additive elements described in the fourth embodimentmay be added to the spin injection layer 30.

Furthermore, the second bias layer 91 can be based on the high-Bs softmagnetic materials described in the first embodiment and materialshaving a negative uniaxial crystalline anisotropy and a laminatedstructure of them.

This time, it was discovered that the magnetization inversion time ofthe spin torque oscillator 10 of the magnetic recording head 5 accordingto this embodiment is 0.35 ns, being the fast inversion. The reason willbe described below. As described in the sixth embodiment, it isessential for the faster magnetization inversion that the second biaslayer 91 is magnetized in a longitudinal direction. An effectiveanisotropy magnetic field in a longitudinal direction consideringcrystalline anisotropy and shape anisotropy can be generally expressedas follows, and the larger this value, longitudinal magnetizationbecomes easier:

Hk _(effective) =Bs(Nd _(perpendicular) −Nd _(longitudinal))+Hk  (3)

where Hk is the crystalline anisotropy magnetic field of the second biaslayer 91 in the longitudinal direction, Bs is the saturation fluxdensity of the second bias layer 91 (that is, 4 nMs taking the saturatedmagnetization of the second bias layer 91 as Ms), Nd_(perpendicular) isthe demagnetizing field coefficient of the second bias layer 91 in theperpendicular direction, Nd_(longitudinal) is the magnetizing fieldcoefficient of the second bias layer 91 in the longitudinal direction.

Nd_(perpendicular)−Nd_(longitudinal) is generally equal to 0.5 or more.Since the saturated magnetization of CoIr used for the second bias layer91 is 1000 emu/cc, Bs (Nd_(perpendicular)−Nd_(longitudinal))=6.3 kOe isobtained. Since the crystalline anisotropy magnetic field of CoIr of thesecond bias layer 91 is −10 kOe in the perpendicular direction, thelongitudinal anisotropy magnetic field can be considered to be Hk=+10kOe effectively in this formula. Consequently, the effective anisotropymagnetic field of the second bias layer 91 is extremely high,Hk_(effective)=16.3 kOe, being easy to be magnetized longitudinally. Asa result, speed enhancement of the magnetization inversion time isallowed.

The reason why the effective anisotropy magnetic field becomes large isthat the crystalline anisotropy magnetic field of CoIr is extremelylarge, 10 kOe, compared with Bs (Nd_(perpendicular)−Nd_(longitudinal)).As described above, when the crystalline anisotropy magnetic field isequal to Bs (Nd_(perpendicular)−Nd_(longitudinal)) or more, thecrystalline anisotropy magnetic field becomes extremely large, allowingthe second bias layer 91 to be magnetized easily in the longitudinaldirection and the magnetization inversion time to be shortened. As aresult, this enables application to a magnetic recording apparatushaving a higher transfer rate.

It is noted that the magnetic recording head according to thisembodiment described above is an example providing the second bias layer91 adjacent to the spin injection layer 30, however the invention is notlimited to this, the bias layer 20 and the third bias layer 92 adjacentto the bias layer 20 may be provided. As a result, the same mechanism asthe second bias layer 91 described above enables speed enhancement ofthe magnetization inversion time.

Eighth Embodiment

Next, an eighth embodiment of the invention will be described.

FIG. 22 is a perspective view illustrating the schematic configurationof a magnetic recording head 5 according to the eighth embodiment of theinvention.

As shown in FIG. 22, the magnetic recording head 5 according to thefifth embodiment of the invention is provided with the shield 62 placedon the trailing side of the main magnetic pole 61, and the spin torqueoscillator 10 is provided between the main magnetic pole 61 and theshield 62. The direction from the main magnetic pole 61 to the shield 62is substantially perpendicular to the lamination direction (thicknessdirection of the layer) of the spin torque oscillator 10. The spininjection layer 30 and the oscillation layer 10 a are magnetizedsubstantially perpendicular to the lamination direction, i.e., in thedirection from the main magnetic pole 61 to the shield 62 or in theopposite direction.

A size of the spin torque oscillator 10 in the vertical direction to thecurrent direction is, for example, a rectangle of 300 Å×500 Å. Theoscillation layer 10 a can be based on, for example, a laminated body ofFeCo with a film thickness of 60 Å and CoFeB with a film thickness of 90Å. The intermediate layer 22 can be made of, for example, Cu with a filmthickness of 30 Å. The spin injection layer 30 can be made of, forexample, CoIr alloy with a thickness of 300 Å. The second bias layer 91can be made of CoPt with a film thickness of 50 Å.

It is noted that the oscillation layer 10 a and the intermediate layer22 can be based on the materials and the laminated structure describedin the first embodiment.

In order to set the spin injection layer 30 to be a single magneticdomain or to be within a recording gap, the film thicknesses of the spininjection layer 30 may be adjusted suitably between 100 Å and 800 Å.

It is noted that the additive elements described in the fourthembodiment may be added to the spin injection layer 30. The second biaslayer 91 may be made of a Co-based hard magnetic alloy such as a CoCralloy or the like.

Furthermore, the spin injection layer 30 and the second bias layer 91may not be laminated directly. The exchange coupling force between theselayers may be adjusted by inserting a nonmagnetic layer.

The magnetization inversion time of the spin injection layer 30 of themagnetic recording head 5 according to this embodiment becomes to be0.25 ns by inserting the bias layer 91, being possible to enhance thespeed of the magnetization inversion. This is the reason why the secondbias layer 91 is magnetized perpendicularly and this magnetizationcauses torque in a perpendicular direction to the magnetization of thespin injection layer 30 through a static magnetic coupling and theexchange coupling.

A condition for the second bias layer 91 to be magnetizedperpendicularly is expressed as follows:

(4)

Hk−Bs(Nd_(perpendicular)−Nd_(longitudinal))>0  (4)

where Hk is the crystalline anisotropy magnetic field of the second biaslayer 91 in the longitudinal direction, Bs is the saturation fluxdensity of the second bias layer 91 (4 nMs taking the saturatedmagnetization of the second bias layer 91 as Ms), Nd_(perpendicular) isthe demagnetizing field coefficient of the second bias layer 91 in theperpendicular direction, Nd_(longitudinal) is the magnetizing fieldcoefficient of the second bias layer 91 in the longitudinal direction.Since Nd_(perpendicular)−Nd_(longitudinal) is generally equal to 0.5 ormore, it is necessary for the crystalline anisotropy magnetic field tobe 0.5 times of the saturation flux density (Bs=4πMs) or more so thatthe second bias layer 91 is magnetized perpendicularly. Satisfaction ofthe condition like this enables the speed enhancement of themagnetization inversion time and application at a higher transfer rate.

It is noted that the magnetic recording head 5 according to thisembodiment described above is an example providing the second bias layer91 adjacent to the spin injection layer 30, however the invention is notlimited to this, the bias layer 20 and the third bias layer 92 adjacentto the bias layer 20 may be provided. As a result, the description abouta characteristic of the second bias layer 91 described above can beapplied to a characteristic of the third bias layer 92.

Ninth Embodiment

Next, a ninth embodiment of the invention will be described.

FIG. 23 is a perspective view illustrating the schematic configurationof a magnetic recording head 5 according to the ninth embodiment of theinvention.

As shown in FIG. 23, the magnetic recording head 5 according to thisembodiment is different from the magnetic recording head illustrated inFIG. 15 in the structure of the spin torque oscillator 10. That is,similar layers serving as the second bias layer 91 and the third biaslayer 92 have a structure laminated in the spin injection layer 30 andthe bias layer 20, respectively.

More specifically, the spin injection layer 30 has an eighth magneticlayer (magnetic layer 96 and magnetic layer 98) and a ninth magneticlayer (magnetic layer 94) laminated on the eighth magnetic layer. Theninth magnetic layer (magnetic layer 97) has a higher magnetic fluxdensity than the eighth magnetic layer (magnetic layer 96 and magneticlayer 98).

Furthermore, the bias layer 20 has a tenth magnetic layer (magneticlayer 93 and magnetic layer 95) and an eleventh magnetic layer (magneticlayer 94) laminated on the tenth magnetic layer. The eleventh magneticlayer (magnetic layer 94) has a higher saturation magnetic flux densitythan the tenth magnetic layer (magnetic layer 93 and magnetic layer 95).

More specifically, the ninth magnetic layer serves as the above secondbias layer 91, and the eleventh magnetic layer serves as the above thirdbias layer 92. As a result, the same effect as the second bias layer 91and the third bias layer 92 described above enables speed enhancement ofthe magnetization inversion time and application at a higher transferrate.

The magnetic recording head 5 illustrated in FIG. 23 is an example thatthe spin injection layer 30 and the bias layer 20 have the laminatedstructure of the eighth magnetic layer and the ninth magnetic layer andthe laminated structure of the tenth magnetic layer and the eleventhmagnetic layer, respectively, however, any one of the spin injectionlayer 30 and the bias layer 20 may have the laminated structure of theeighth magnetic layer and the ninth magnetic layer or the laminatedstructure of the tenth magnetic layer and the eleventh magnetic layer.

The magnetic recording head 5 illustrated in FIG. 23 has the spininjection layer 30 having the structure of the ninth magnetic layer(magnetic layer 97) sandwiched by the two eighth magnetic layer(magnetic layer 96, 98), however, the eighth magnetic layer may be asingle layer, the ninth magnetic layer being laminated on the singleeighth magnetic layer. Similarly, the tenth magnetic layer may be asingle layer, the eleventh magnetic layer being laminated on the tenthmagnetic layer.

Furthermore, at least any one of the spin injection layer 30 and thebias layer 20 may be provided with the laminated structure of the eighthmagnetic layer and the ninth magnetic layer oar the laminated structureof the tenth magnetic layer and the eleventh magnetic layer described inthis embodiment, and simultaneously any one of the second bias layer 91and the third bias layer 92 described in the sixth embodiment may beprovided.

Furthermore, the structure having the eighth, the ninth, the tenth andthe eleventh magnetic layer described in this embodiment and thestructure having the second, the third bias layer, and the materialsdescribed in the fourth, the fifth embodiments may be simultaneouslyused.

Tenth Embodiment

Next, a magnetic recording apparatus according to an embodiment of theinvention is described. More specifically, the magnetic recording head 5of the invention described with reference to FIGS. 1-4, 6-7 and 10-23 isillustratively incorporated in an integrated recording-reproducingmagnetic head assembly, which can be installed on a magneticrecording/reproducing apparatus.

FIG. 24 is a principal perspective view illustrating the schematicconfiguration of such a magnetic recording/reproducing apparatus.

More specifically, the magnetic recording/reproducing apparatus 150 ofthe invention is an apparatus based on a rotary actuator. In thisfigure, a recording medium disk (medium disk) 180 is mounted on aspindle 152 and rotated in the direction of arrow A by a motor, notshown, in response to a control signal from a drive controller, notshown. The magnetic recording/reproducing apparatus 150 of the inventionmay include a plurality of medium disks 180.

A head slider 3 for recording/reproducing information stored on themedium disk 180 has a configuration as described above with reference toFIG. 2 and is attached to the tip of a thin-film suspension 154. Here, amagnetic recording head according to any one of the above embodiments isillustratively installed near the tip of the head slider 3.

When the medium disk 180 is rotated, the air bearing surface (ABS) 100of the head slider 3 is held at a prescribed floating amount from thesurface of the medium disk 180. Alternatively, it is also possible touse a slider of the so-called “contact-traveling type”, where the slideris in contact with the medium disk 180.

The suspension 154 is connected to one end of an actuator arm 155including a bobbin for holding a driving coil, not shown. A voice coilmotor 156, which is a kind of linear motor, is provided on the other endof the actuator arm 155. The voice coil motor 156 is composed of thedriving coil, not shown, wound up around the bobbin of the actuator arm155 and a magnetic circuit including a permanent magnet and an opposedyoke disposed so as to sandwich the coil therebetween.

The actuator arm 155 is held by ball bearings, not shown, provided attwo positions above and below the spindle 157, and can be slidablyrotated by the voice coil motor 156.

FIG. 25 is an enlarged perspective view of the magnetic head assembly160 ahead of the actuator arm 155 as viewed from the disk side. Morespecifically, the magnetic head assembly 160 has an actuator arm 155illustratively including a bobbin for holding a driving coil, and asuspension 154 is connected to one end of the actuator arm 155.

To the tip of the suspension 154 is attached a head slider including anyone of the magnetic recording heads 5 described above with reference toFIGS. 1-4, 6-23. The suspension 154 has a lead 164 for writing andreading signals. The lead 164 is electrically connected to eachelectrode of the magnetic head incorporated in the head slider 3. In thefigure, the reference numeral 165 denotes an electrode pad of themagnetic head assembly 160.

According to the invention, by using the magnetic recording head asdescribed above with reference to FIGS. 1-4, 6-23, it is possible toreliably record information on the perpendicular magnetic recordingmedium disk 180 with higher recording density than conventional. Here,for effective microwave assisted magnetic recording, preferably, theresonance frequency of the medium disk 180 to be used is nearly equal tothe oscillation frequency of the spin torque oscillator 10.

FIG. 26 is a schematic view illustrating a magnetic recording mediumthat can be used in this embodiment.

More specifically, the magnetic recording medium 1 of this embodimentincludes perpendicularly oriented, multiparticle magnetic discretetracks (recording track) 86 separated from each other by a nonmagneticmaterial (or air) 87. When this medium 1 is rotated by a spindle motor 4and moved toward the medium moving direction 85, a recordingmagnetization 84 can be produced by the magnetic recording head 5described above with reference to FIGS. 1-4, 6-23.

By setting the width (TS) of the spin torque oscillator 10 in the widthdirection of the recording track to not less than the width (TW) of therecording track 86 and not more than the recording track pitch (TP), itis possible to significantly prevent the decrease of coercivity inadjacent recording tracks due to leaked high-frequency magnetic fieldfrom the spin torque oscillator 10. Hence, in the magnetic recordingmedium 1 of this example, only the recording track 86 to be recorded canbe effectively subjected to microwave assisted magnetic recording.

According to this embodiment, a microwave assisted magnetic recordingapparatus with narrow tracks, i.e. high track density, is realized moreeasily than in the case of using a multiparticle perpendicular mediummade of the so-called “blanket film”. Furthermore, by using themicrowave assisted magnetic recording scheme and using a magnetic mediummaterial with high magnetic anisotropy energy (Ku) such as FePt or SmCo,which cannot be written by conventional magnetic recording heads,magnetic medium particles can be further downscaled to the size ofnanometers. Thus it is possible to realize a magnetic recordingapparatus having far higher linear recording density than conventionalalso in the recording track direction (bit direction).

FIG. 27 is a schematic view illustrating another magnetic recordingmedium that can be used in this embodiment.

More specifically, the magnetic recording medium 1 of this exampleincludes magnetic discrete bits 88 separated from each other by anonmagnetic material 87. When this medium 1 is rotated by a spindlemotor 4 and moved toward the medium moving direction 85, a recordingmagnetization 84 can be produced by the magnetic recording head 5described above with reference to FIGS. 1-4, 6-23.

According to the invention, as shown in FIGS. 17 and 18, recording canbe reliably performed also on the recording layer having high coercivityin a discrete-type magnetic recording medium 1, allowing magneticrecording with high density and high speed.

Also in this example, by setting the width (TS) of the spin torqueoscillator 10 in the width direction of the recording track to not lessthan the width (TW) of the recording track 86 and not more than therecording track pitch (TP), it is possible to significantly prevent thedecrease of coercivity in adjacent recording tracks due to leakedhigh-frequency magnetic field from the spin torque oscillator 10. Henceonly the recording track 86 to be recorded can be effectively subjectedto microwave assisted magnetic recording. According to this example, bydownscaling the magnetic discrete bit 88 and increasing its magneticanisotropy energy (Ku), there is a possibility of realizing a microwaveassisted magnetic recording apparatus having a recording density of 10Tbits/inch² or more as long as thermal fluctuation resistance under theoperating environment can be maintained.

The embodiments of the invention have been described with reference tothe examples. However, the invention is not limited to the aboveexamples. For instance, two or more of the examples described above withreference to FIGS. 1-4, 6-7, 10-27 can be combined as long astechnically feasible, and such combinations are also encompassed withinthe scope of the invention.

That is, the invention is not limited to the examples, but can bepracticed in various modifications without departing from the spirit ofthe invention, and such modifications are all encompassed within thescope of the invention.

1. A magnetic writing head comprising: a main magnetic pole; a laminatedbody including a first magnetic layer having a coercivity lower than amagnetic field applied by the main magnetic pole, and a second magneticlayer having a coercivity lower than the magnetic field applied by themain magnetic pole; and a pair of electrodes operable to pass a currentthrough the laminated body.
 2. The magnetic writing head according toclaim 1, wherein the first magnetic layer and the second magnetic layerare laminated substantially perpendicular to a medium moving direction.3. The magnetic writing head according to claim 1, wherein the firstmagnetic layer and the second magnetic layer are laminated substantiallyparallel to a medium moving direction.
 4. The magnetic writing headaccording to claim 1, wherein the coercivity of the first magnetic layeris lower than the coercivity of the second magnetic layer, and a currentis passed from the second magnetic layer to the first magnetic layer viathe pair of electrodes.
 5. The magnetic writing head according to claim1, further comprising a shield, wherein the laminated body is sandwichedbetween the shield and the main magnetic pole.
 6. The magnetic writinghead according to claim 1, wherein the laminated body further includes athird magnetic layer provided between one of the electrodes and thefirst magnetic layer, the electrode is located at the opposite side ofthe first magnetic layer as the second magnetic layer, and the thirdmagnetic layer has a coercivity lower than the magnetic field applied bythe main magnetic pole.
 7. The magnetic writing head according to claim6, wherein the third magnetic layer contains at least one elementselected from a group consisting of Ru, W, Re, Os, Ir, Sm, Eu, Tb, Gd,Dy, Ho, Rh and Pd.
 8. The magnetic writing head according to claim 6,wherein one of the pair of electrodes which is nearer to the thirdmagnetic layer than the other of the electrodes contains at least oneelement selected from a group consisting of Ru, Rh, Pd, Ir and Pt. 9.The magnetic writing head according to claim 6, wherein the laminatedbody further includes a fourth magnetic layer adjacent to the thirdmagnetic layer, the third magnetic layer is provided between the fourthmagnetic layer and the first magnetic layer, and an easy magnetizationaxis of the fourth magnetic layer is substantially perpendicular to anormal line of a surface of the main magnetic pole facing the laminatedbody.
 10. The magnetic writing head according to claim 6, wherein thethird magnetic layer includes a fourth magnetic layer and a fifthmagnetic layer laminated on the fourth magnetic layer, and thesaturation magnetic flux density of the fifth magnetic layer is higherthan the saturation magnetic flux density of the fourth magnetic layer.11. The magnetic writing head according to claim 1, wherein the secondmagnetic layer contains at least one element selected from a groupconsisting of Ru, W, Re, Os, Ir, Sm, Eu, Tb, Gd, Dy, Ho, Rh and Pd. 12.The magnetic writing head according to claim 1, wherein one of the pairof electrodes which is nearer to the second magnetic layer than theother of the electrodes contains at least one element selected from agroup consisting of Ru, Rh, Pd, Ir and Pt.
 13. The magnetic writing headaccording to claim 1, wherein the second magnetic layer includes a thirdmagnetic layer and a fourth magnetic layer laminated on the thirdmagnetic layer, and the saturation magnetic flux density of the fourthmagnetic layer is higher than the saturation magnetic flux density ofthe third magnetic layer.
 14. A magnetic recording apparatus comprising:a magnetic recording medium; a magnetic writing head according to claim1, a moving mechanism configured to allow relative movement between themagnetic recording medium and the magnetic writing head which areopposed to each other with a spacing therebetween or in contact witheach other; a controller configured to position the magnetic writinghead at a prescribed recording position of the magnetic recordingmedium; and a signal processing unit configured to perform writing of asignal on the magnetic recording medium by using the magnetic writinghead.
 15. A magnetic recording and reproducing head comprising: awriting head section including: a main magnetic pole configured to applya magnetic field to control a direction of a magnetization of a magneticrecording layer of a magnetic recording medium; a laminated bodyincluding a first magnetic layer having a coercivity lower than amagnetic field applied by the main magnetic pole, and a second magneticlayer having a coercivity lower than the magnetic field applied by themain magnetic pole; and a pair of electrodes operable to pass a currentthrough the laminated body; and a reproducing head section including: afirst magnetic shield layer; a second magnetic shield layer; and amagnetic reproducing device provided between the first magnetic shieldlayer and the second magnetic shield layer, the magnetic reproducingdevice being configured to read a direction of a magnetization of themagnetic recording layer.
 16. The magnetic recording and reproducinghead according to claim 15, wherein the first magnetic layer and thesecond magnetic layer are laminated substantially parallel to a mediummoving direction of the magnetic recording medium.
 17. The magneticrecording and reproducing head according to claim 15, wherein thecoercivity of the first magnetic layer is lower than the coercivity ofthe second magnetic layer, and a current is passed from the secondmagnetic layer to the first magnetic layer via the pair of electrodes.18. The magnetic recording and reproducing head according to claim 15,wherein the writing head section further includes a third magneticshield, and the laminated body is sandwiched between the third magneticshield and the main magnetic pole.
 19. The magnetic recording andreproducing head according to claim 15, wherein the writing head sectionfurther includes an intermediate layer provided between the firstmagnetic layer and the second magnetic layer.
 20. A magnetic recordingand reproducing head comprising: a writing head section including: amain magnetic pole configured to apply a magnetic field to control adirection of a magnetization of a magnetic recording layer of a magneticrecording medium; a laminated body including a first magnetic layerhaving a coercivity lower than a magnetic field applied by the mainmagnetic pole, and a second magnetic layer having a coercivity lowerthan the magnetic field applied by the main magnetic pole, thecoercivity of the first magnetic layer being lower than the coercivityof the second magnetic layer; and a pair of electrodes operable to passa current through the laminated body; and a reproducing head sectionincluding: a first magnetic shield layer; a second magnetic shieldlayer; and a magnetic reproducing device provided between the firstmagnetic shield layer and the second magnetic shield layer, the magneticreproducing device being configured to read a direction of amagnetization of the magnetic recording layer.
 21. The magneticrecording and reproducing head according to claim 20, wherein thewriting head section further includes an intermediate layer providedbetween the first magnetic layer and the second magnetic layer.
 22. Themagnetic recording and reproducing head according to claim 20, whereinthe first magnetic layer and the second magnetic layer are laminatedsubstantially parallel to a medium moving direction of the magneticrecording medium.
 23. The magnetic recording and reproducing headaccording to claim 20, wherein a current is passed from the secondmagnetic layer to the first magnetic layer via the pair of electrodes.24. The magnetic recording and reproducing head according to claim 20,wherein the writing head section further includes a third magneticshield, and the laminated body is sandwiched between the third magneticshield and the main magnetic pole.